CORAL CONGLOMERATES AS MARKERS OF PAST ENVIRONMENTS

On the reefs of the central Pacific, emerged coral conglomerates give evidence of ancient sheets of reefal debris deposited above reef flats , which were subsequently lithified and exposed by a fall in the relat ive sea level. Such spreadings of debris, which contribute to the stre ngthening of the reef framework structure, are generally produced by h igh-energy waves, often during storm surges. Examples are described of former spreadings which occurred in the sublittoral, intertidal, and partially supralittoral zones. According to the distribution of coral conglomerates over the reefs, it is possible to identify the areas whi ch were most exposed to storm waves and therefore to specify locally t he trajectory of ancient tropical cyclones. In the Leeward Islands of the Society Archipelago, the most significant cyclones came mostly fro m the west between 3000 and 1600 yr B.P., when the relative sea level was almost Im above the present one.